Influence of the amino acid sequence and nature of the cyclodextrin on the separation of small peptide enantiomers by capillary electrophoresis using α-, β-, and γ-cyclodextrin and the corresponding hydroxypropyl derivatives

The separation of the LL and DD enantiomers of dipeptides and tripeptides using α-, β-, and γ-cyclodextrins as well as the corresponding hydroxypropyl derivatives was studied with respect to the amino acid sequence of the peptides and the nature of the cyclodextrins. Standardized conditions regarding buffer pH and molarity, cyclodextrin concentration, and separation voltage were applied. α-Cyclodextrin, hydroxypropyl-α-cyclodextrin, β-cyclodextrin, and hydroxypropyl-β-cyclodextrin were the more universal cyclodextrins for enantioseparations of the investigated set of peptides compared to γ-cyclodextrin and hydroxypropyl-γ-cyclodextrin. The enantiomer migration order depended both on the cyclodextrin and on the amino acid sequence of the peptide. Reversal of the enantiomer migration order upon increasing the buffer pH from 2.5 to 3.5 was observed in some cases using β-cyclodextrin.